Without limiting the scope of the present invention, its background will be described with reference to producing fluid from a subterranean formation, as an example.
After drilling each of the sections of a subterranean wellbore, individual lengths of relatively large diameter metal tubulars are typically secured together to form a casing string that is positioned within each section of the wellbore and cemented in place. This casing string is used to increase the integrity of the wellbore by preventing the wall of the hole from collapsing and to prevent movement of fluids from one formation to another formation.
After well construction is finished, the completion process begins. The completion process comprises numerous steps that include creating hydraulic openings or perforations that extend through the production casing string and the cement, as well as a short distance into the desired formation or formations, so that production fluids can enter the interior of the wellbore. In addition, the completion process may involve formation stimulation to enhance production, installation of sand control devices to prevent sand production and the like. The completion process also includes installing a production tubing string within the well casing. Unlike the casing string that forms a part of the wellbore itself, the production tubing string is used to produce the well by providing the conduit for formation fluids to travel from the formation depth to the surface.
Typically, the production tubing string extends from the surface to the formations traversed by the well and includes one or more production seal assemblies. The purpose of the seal assemblies is to support the production tubing and other completion equipment and to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the seal assembly locations. Commonly, multiple seal assemblies are utilized within a tubing string such that multiple formations or multiple zones within a formation can be isolated from one another. Such isolation allows formation or zone specific treatment regimens to be performed. In addition, such isolation allows more precise control over the production from the well.
A number of problems may occur during the installation and use of traditional seal assemblies. For example, the elastomeric material in the seal assembly can extrude into undesired regions due to high stress, faulty design or extreme wellbore conditions. In addition, other problems associated with traditional seal assemblies include premature setting, incomplete setting and loss of long term sealing capacity.
To overcome these and other problems associated with traditional seal assemblies, test wells and laboratory facilities are commonly used to perform testing of seal assembly designs. For example, in order to perform certain testing of the mechanical operation and responses of a seal assembly design, the seal assemblies are placed inside a section of well casing for testing. While valuable information can be obtained using such testing methods, aspects of the mechanical response of the elastomeric elements within a seal assembly remain difficult to directly observe. In addition, it has been found that the temperatures and the large deformations to which the elastomeric seal elements are subjected do not allow the use of traditional strain sensors. Specifically, available strain sensors are limited by maximum temperature, maximum strain or both.
Therefore, a need has arisen for a system and method of monitoring the mechanical response of the elastomeric elements within a downhole seal assembly during installation and operation of the downhole seal assembly. A need has also arisen for such a system and method wherein the sensors used to monitor the mechanical response of the elastomeric elements can withstand the temperatures and strains encountered in the downhole operating environment of the downhole seal assembly. Further, a need has arisen for such a system and method of monitoring the mechanical response of the elastomeric elements within a downhole seal assembly during the design and testing of downhole seal assemblies.